1. Field of the Invention
This invention relates an improved ophthalmological instrument and phaco tip device used in the removal of a cataract nucleus from an eye and an improved cataract removal method.
2. Background Discussion
The current technology for cataract removal involves the use of ultrasound to dissolve, that is, emulsify, the nucleus, the hardest part of a cataract. This approach allows the cataract nucleus to be removed by washing it out through a tiny incision as small as 3 millimeters (mm) or less. Having a small incision allows safer surgery and rapid recovery. The one drawback to this technique is that exposure to ultrasonic energy needs to be kept to a minimum. Excess exposure causes damage to the very sensitive cornea. The chance of this happening is more likely when a cataract is dense or very hard. Long ultrasonic time exposures when trying to emulsify dense cataract nuclei may result in corneal damage and other complications.
It has been found that if the nucleus can first be segmented into smaller pieces, such as quarters, the ultrasonic exposure time can be greatly reduced even for very dense cataracts. The simplest approach to quartering the nucleus has been to use the regular ultrasonic emulsifier to cut a deep groove in the middle of the nucleus in an anterior posterior direction. The nucleus is then rotated 90 degrees and another groove cut deeply at right angles to the first groove, thus creating a xe2x80x9ccrossxe2x80x9d pattern. Typically these grooves are about 1 to 1.5 millimeters in width and 3 millimeters deep, and intersect at about the center of the nucleus. Using a cracking device such as Katena nucleus splitters, the nucleus is then split into four quarters and each quarter removed by ultrasonic emulsification. A conventional phaco tip using ultrasonic energy for cutting these grooves comprises a hollow needle, having a passageway with a 1 mm to 1.5 mm diameter. Thus, the groove being cut is also equal to the tip diameter and is about 1 mm to 1.5 mm wide. The central opening in the ultrasonic tip is used to aspirate the emulsified and liquefied nucleus out of the eye as the emulsification proceeds.
Because the phaco tips used so far are 1 mm to 1.5 mm wide, the ultrasonic energy expended to cut through very hard nucleus is excessive, thus occasionally causing severe damage to the cornea. Also the nucleus may be too hard and simply not be able to be cut with such a conventional phaco tip. Thus, there may at times be a risk of dislocating the entire nucleus into the posterior region of the eye. Often under such conditions the ultrasonic procedure has to be abandoned and the surgeon has to resort to the old fashioned technique of opening the eye extensively with a knife to extract the cataract in its entirety, leading to a complicated prolonged surgical outcome.
In order to circumvent these above difficulties, Dr. Nagahara some years ago developed the concept of xe2x80x9cnatural cleavage planesxe2x80x9d existing in the nucleus that could be used to advantage to essentially split (or chop, as he called it) the nucleus into two pieces by simply pushing a hook through the nucleus center. Although this technique has been popularized in the last few years, many surgeons still find it very difficult to use reliably.
More recently, a pre-chopper was introduced by Dr. Akoshi. The idea behind this pre-chopper was to make a very sharp pointed set of paddles in the form of a cross action forceps that could be pushed into the center of the nucleus and then pressed apart against each other, thus splitting the nucleus into 2 pieces. The difficulty has been that this pre-chopper only works well when the nucleus has a density neither too hard nor too soft. If the nucleus happens to be very soft, the paddles simply cause the nucleus material to get xe2x80x9cmushedxe2x80x9d without a splitting action. If the nucleus is anywhere too hard, the pre-chopper cannot be pushed into its center, deeply enough to split the nucleus. There is a serious risk of dislocation of the nucleus if further pressure is exerted. Very hard nucleus that will require excessive ultrasonic time exposure cannot be split with a pre-chopper.
All current phaco manufacturers have focused on making phaco machines more and more sophisticated with more available ultrasonic power, more vacuum, more pedals, and other features. Considering the steps involved in one of the more popular approaches to nucleus removal, the groove and crack approach, there are clearly at least two distinct steps involved that require the use of ultrasonic energy. The first step is to break the nucleus into smaller segments (usually quarters) and then to debulk, or remove each piece by emulsification. Breaking the nucleus into segments is achieved by deeply grooving the nucleus and then cracking the nucleus manually either with the standard phaco handpiece and another instrument (2 handed approach) or with a nucleus cracker (Katena, Rhein, etc.) in a one handed approach. The debulking step is performed with the same phaco tip used for making the initial grooves. It is a very inefficient in breaking the nucleus and debulking.
There are several disadvantages in using a standard single tip approach. Using one standard tip for both grooving the nucleus and debulking the segments is a very inefficient approach. In soft nuclei this approach manages to work, but when faced with a very hard nucleus, even a 45 degree beveled tip or a Kelman tip can take several minutes of phaco time to cut a groove deep enough. This also puts severe stress on the zonules. A phaco tip designed primarily for debulking, as all current tips are, works poorly as a cutting tool. To attempt to enhance the cutting action, manufacturers have advocated putting a 30 or 45 degree bevel to the tip. This improves the cutting characteristics of the tip, but exposes the cornea endothelial to excessive ultrasonic energy being released from the bevel face up position that is currently advocated. All currently available tips are 1-1.5 mm in diameter to allow for adequate aspiration of the released debris. When such a tip is used initially to just cut a groove, only the apex of the beveled tip is in contact with and is actually cutting nucleus. The greater portion of the face of the vibrating tip is in aqueous with the bevel facing upwards, thus transmitting most of the ultrasonic energy directly towards the cornea endothelium. Since the conventional phaco tip has ongoing aspiration, the tip has to be used with the bevel face up, thus directing a large part of the ultrasonic energy directly towards the corneal endothelium rather than into the cataract nucleus that needs to be cut.
This invention has several features, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this invention as expressed by the claims that follow, its more prominent features will now be discussed briefly. After considering this discussion, and particularly after reading the section entitled, xe2x80x9cDETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS,xe2x80x9d one will understand how the features of this invention provide its benefits, which include, but are not limited to, safer surgical techniques, greater control by the surgeon during cataract removal, and reduction in damage to tissue during surgery.
This invention includes an ophthalmological device for cutting into a nucleus of a cataract. It employs a unique phaco tip. The first feature of this ophthalmological device is that the phaco tip has a body with a solid blade at its distal end. The solid blade has a face edge adapted to be placed in contact with the nucleus. This face edge is characterized in that it does not have any aspiration port therein. The face edge preferably has a surface area from about 0.4 to about 0.8 square millimeters, and a thickness from about 0.01 to about 0.6 millimeters. The width and height dimensions of the face edge at their greatest dimensions do not exceed the width and height dimensions of the body of the phaco tip.
The second feature is that the blade has a length which does not exceed 5.0 millimeters, preferably having a length of from about 2.0 to about 5.0 millimeters, a height which does not exceed 3.0 millimeters, preferably having a height of from about 1.0 to about 3.0 millimeters, and a thickness which does not exceed 0.6 millimeter, preferably having a thickness of from about 0.1 to about 0.6 millimeters.
The third feature is that the body has an aspiration port therein displaced rearward from the face edge by a distance greater than the length of the blade. This aspiration port is positioned on the body to point away from the nucleus when the face edge is placed in contact with the nucleus. A sleeve fits over the body of the phaco tip and has a forward section that terminates in an opening in advance of the aspiration port, so that the sleeve does not cover the aspiration port.
The fourth feature is that the blade may be beveled or blunt. When beveled, the bevel is at an angle from about 30xc2x0 to about 45xc2x0. The blade may also have different shapes, for example, a chisel shape or a claw shape.
This invention also includes a surgical instrument for removing a nucleus of a cataract from beneath the cornea of an eye. The instrument comprises a source of aspiration, and a handpiece including phaco tip having a face edge adapted to be placed in contact with the nucleus. The face edge has aspiration port therein that is adapted to be placed in communication with the source of aspiration. A control unit regulates the application of aspiration to the aspiration port, enabling aspiration at the aspiration port to be turned on and off on command. This instrument allows the surgeon to only apply aspiration when needed. Consequently, aspiration is turned off when cracking the nucleus.
This instrument is made by modifying a conventional phaco control unit so that it includes a manually operable control element such as a switch that enables a surgeon to selectively turn on and off aspiration at the phaco tip. Preferably, a switch is incorporated in a foot pedal. Employing the xe2x80x9cgroove and crackxe2x80x9d approach, using either the unique phaco tip of this invention or a conventional phaco tip to crack the nucleus, the surgeon selectively turns aspiration on and off, drawing cataract debris into the aspiration passageway.
This invention also includes methods of removing a nucleus of a cataract from beneath the cornea of an eye.
One method includes:
(a) making an opening in the eye to provide access to the nucleus and allow insertion through the opening of a distal end of a first phaco tip having a solid blade with a face edge adapted to be placed in contact with the nucleus, said face edge characterized in that it does not have any aspiration port therein,
(b) inserting the blade of the first phaco tip through the opening and providing ultrasonic energy to the blade while making at least one incision with the blade in the nucleus, said incision having internal walls,
(c) cracking the nucleus by inserting into the incisions an instrument which is manually manipulated to apply pressure against the internal walls of the incision to break the nucleus into segments, and
(d) inserting through the opening a second phaco tip including an aspiration port therein and applying aspiration while emulsifying the segments and withdrawing the emulsified segments through the aspiration port.
This one method may include irrigating the nucleus with water, which exits through the opening.
Another method includes:
(a) making an opening in the eye to provide access to the nucleus and allow insertion through the opening of a distal end of a phaco tip having a face edge adapted to be placed in contact with the nucleus, said face edge having and aspiration port therein, said aspiration port being in communication with a source of aspiration that can be selectably applied and discontinued under the control of a surgeon conducting the method,
(b) inserting the blade of the phaco tip through the opening and providing ultrasonic energy to the blade while making at least one incision with the blade in the nucleus and simultaneously discontinuing aspiration as the incision is being made, said incision having internal walls,
(c) cracking the nucleus by inserting into the incisions an instrument which is manually manipulated to apply pressure against the internal walls of the incision to break the nucleus into segments, and
(d) applying aspiration to the aspiration port while emulsifying the segments and withdrawing the emulsified segments through the aspiration port.
In practicing the above methods the surgeon makes a cross incision having a depth that does not to exceed about 3 millimeters, and the nucleus is mobilized so that it may be rotated substantially 90 degrees. The eye is irrigated with fluid flowing out the sleeve, over the nucleus, and exiting through the corneal opening.